Inorganic pigments such as iron oxides, zinc oxide, talc, titanium oxide, chromium hydroxide, chromium oxide, ferric ammonium ferrocyanide, manganese ammonium pyrophosphate complex (manganese violet), and sodium aluminum sulfosilicates complex (ultramarine blue) are commonly used as cosmetic ingredients. The current methods for pigment dispersion in a cosmetic preparation usually require a series of steps including particle size reduction of a pigment, dispersing the pigment into a liquid base or the total formulation under high shear mixing, and then subjecting the preformulated base or formulation to further homogenization to yield a final product.
Due to the high specific gravity of an inorganic pigment, the pigment tends to settle in a liquid base over a period of time. Furthermore, the pigment materials dispersed in a liquid base may be adversely affected by the liquid vehicle, entrapped air or other ingredients and result in color changes or discoloration. Thus the dispersibility of a pigment material and the color stability of a pigment dispersion may seriously affect the quality of a cosmetic preparation. The ease of processing a pigment is also very desirable in the overall process.
Treatment of pigment surfaces in general is known in the field of coating, cosmetics and ink technology. The art of pigment dispersion is generally taught in a textbook by T. C. Patton, titled "Paint Flow and Pigment Dispersion", 2nd ed. Wiley Interscience, New York, 1978. Specific examples in the prior art where pigment surface treatment is taught can be found in Japanese Patents 86,007,227; 55,007,212; 81,043,264; 86,058,499; 58,096,009; and 81,034,232; and U.S. Pat. Nos. 4,520,153; 4,063,957, and 4,305,853. In addition, U.S. Pat. Nos. 4,704,309 and 4,847,316 teach milling of pigments with an aqueous dispersion of polyester material.
It would be desirable to have a process, and the compositions prepared therefrom, for the preparation of a pigment blend which exhibits good dispersibility in aqueous or selected polar solvent systems and is easy to process.